fabi/Xenia-Canary
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

[Thread/Posix] Fix thread suspend deadlock

Browse Source 
Replace std::mutex/condition_variable with sem_wait/sem_post for thread
suspension, as WaitSuspended is called from the SIGRTMIN signal handler
where pthread_mutex_lock is not async-signal-safe.
This commit is contained in:
Herman S.
2026-03-10 21:44:30 +09:00
parent 4f1394bbaa
commit 6f18c98502
1 changed files with 21 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files

28
src/xenia/base/threading_posix.cc
View File

@@ -16,6 +16,7 @@
#include <pthread.h>
#include <sched.h>
#include <semaphore.h>
#include <signal.h>
#include <sys/syscall.h>
#include <unistd.h>
@@ -572,6 +573,7 @@ class PosixCondition<Thread> final : public PosixConditionBase {
exit_code_(0),
state_(State::kUninitialized),
suspend_count_(0) {
sem_init(&suspend_sem_, 0, 0);
#if XE_PLATFORM_ANDROID
android_pre_api_26_name_[0] = '\0';
#endif
@@ -613,6 +615,7 @@ class PosixCondition<Thread> final : public PosixConditionBase {
exit_code_(0),
state_(State::kRunning),
suspend_count_(0) {
sem_init(&suspend_sem_, 0, 0);
#if XE_PLATFORM_ANDROID
android_pre_api_26_name_[0] = '\0';
#endif
@@ -802,9 +805,13 @@ class PosixCondition<Thread> final : public PosixConditionBase {
*out_previous_suspend_count = suspend_count_;
}
--suspend_count_;
// If suspend count reaches 0, transition to running
// If suspend count reaches 0, transition to running and wake the thread
if (suspend_count_ == 0 && state_ == State::kSuspended) {
state_ = State::kRunning;
// Post to the semaphore to wake the thread from WaitSuspended.
// sem_post is async-signal-safe, so this is safe even if called
// from unusual contexts.
sem_post(&suspend_sem_);
}
state_signal_.notify_all();
return true;
@@ -830,8 +837,8 @@ class PosixCondition<Thread> final : public PosixConditionBase {
if (is_current_thread) {
// Self-suspension: Instead of sending a signal, directly call
// WaitSuspended This avoids the signal handler complexity for the
// self-suspend case
// WaitSuspended. This avoids the signal handler complexity for the
// self-suspend case.
WaitSuspended();
return true;
}
@@ -887,11 +894,16 @@ class PosixCondition<Thread> final : public PosixConditionBase {
[this] { return state_ != State::kUninitialized; });
}
/// Set state to suspended and wait until it reset by another thread
/// Set state to suspended and wait until it is reset by another thread.
/// Uses sem_wait which is async-signal-safe, allowing this to be called
/// from a signal handler (e.g., the SIGRTMIN suspend signal handler)
/// without risking deadlock or heap corruption from non-reentrant
/// mutex/condvar operations.
void WaitSuspended() {
std::unique_lock lock(state_mutex_);
state_signal_.wait(lock, [this] { return suspend_count_ == 0; });
state_ = State::kRunning;
int ret;
do {
ret = sem_wait(&suspend_sem_);
} while (ret == -1 && errno == EINTR);
}
void* native_handle() const override {
@@ -905,12 +917,14 @@ class PosixCondition<Thread> final : public PosixConditionBase {
if (thread_) {
pthread_join(thread_, nullptr);
}
sem_destroy(&suspend_sem_);
}
pthread_t thread_;
bool signaled_;
int exit_code_;
State state_; // Protected by state_mutex_
uint32_t suspend_count_; // Protected by state_mutex_
sem_t suspend_sem_; // Async-signal-safe suspend/resume semaphore
mutable std::mutex state_mutex_;
mutable std::mutex callback_mutex_;
mutable std::condition_variable state_signal_;